Fluid absorber for a suction tube set

ABSTRACT

The suction tube set employs a compressed cellulosic sponge mass as a fluid absorber in the suction line for absorbing an amount of fluid, for example 1.5 cc, without any significant increase in resistance to air flow. The compressed sponge mass is secured in place within a tubular housing of the suction tube set with a gap formed between each end of the sponge mass and an end cap of the housing to avoid blockage of air flow.

This application is a division of Ser. No. 09/326,269, filed Jun. 7,1999 now U.S. Pat. No. 6,254,590B1.

This invention relates to a fluid absorber for a suction tube set. Moreparticularly, this invention relates to a fluid absorber for a suctiontube set for use in laser eye surgery.

As is known, various types of devices and equipment have been utilizedin surgical procedures performed on an eyeball and particularly forphotoretractive keratectomy laser surgery. During such procedures, aweak laser beam is used to remove tiny layers of tissue and to reshapethe cornea to improve sight. Typically, photoretractive keratectomy isaccomplished by an excimer laser beam that ablates away corneal tissuein a photodecomposition process. Before this occurs, a flap of theepithelium of the cornea is surgically removed to expose Bowman's layeron the anterior surface of the stroma. The excimer laser beam is thenused for laser ablation at Bowman's layer. The laser beam is also usedto remove corneal tissue to varying depths as necessary forre-contouring the anterior stroma. Afterward, the epithelium flap isrepositioned to rapidly regrow and resurface the contoured area.

In order to stabilize an eyeball for purposes of such a surgical laseroperation, it has been known to fix the eyeball in place using a suctiondevice. This allows a surgeon to operate on the eyeball without the riskthat the eyeball may move during the operation.

One known device for stabilizing an eyeball and for effecting removal ofan epithelium flap is an automated disposable keratome sold byLaserSight Technologies, Inc. of Winter Park, Fla. This instrumentprovides a ring which is to be placed on the eyeball as well as akeratome for slicing a flap in the epithelium of the eyeball. Once thering is in place with suction on, the keratome can be operated by asurgeon to cut the flap. High suction is generally required briefly toraise the LOP (intraocular pressure) and keep the eye rigid so that aclean cut can be made. However, there is a danger involved with suchinstruments if there is a loss of suction during this cutting time.Accordingly, the instrument is provided with an alarm that warns asurgeon instantly if suction is lost.

Studies have shown that the IOP rises to over 99 mmHg at maximumsuction, with the estimated actual IOP during maximum suction being ashigh as 130 or 140 mmHg. However, prolonged exposure to this level ofIOP creates a potential for damage to delicate retinal structures. Thus,in order to preclude damage, the time of exposure to high vacuum islimited to an absolute minimum.

Thus, with the suction ring in place and the vacuum set at 5 inches ofmercury (Hg), the patient's IOP rises to the 30-35 mmHg range. Thisrelatively safe level of vacuum is enough to hold the ring in place butnot enough to produce a good cut. So when the surgeon activates thekeratome, the vacuum rises immediately to 24 inches of mercury, pushingthe IOP high enough for a good cut. However, the high vacuum lasts onlyfor the 2 to 3 seconds required for the keratome to go forward acrossthe ring. When the keratome goes back, the vacuum drops down again to 5inches Hg, enough to hold the ring in place but not enough to endangerthe retina and optic nerve.

Another problem which arises during an eye operation of the above typeis due to the fact that tearing of the eyeball usually occurs so thatfluid, i.e. salt water, is drawn into the suction ring and eventuallyinto the vacuum pump. Should fluid begin to enter the vacuum pump, thepump can cease to draw a vacuum so that the eyeball is no longer lockedin place. This is particularly the case where the pump retains fluidfrom a succession of eye operations.

In order to prevent fluids from migrating into the vacuum pump, fluidtraps have been incorporated in the suction line between the vacuum pumpand eyeball-engaging ring. That is to say, the line from the ringterminates in a vertically disposed trap to deliver fluid into the trapwhile a second line extends from the trap to the vacuum pump in order toconduct a vacuum force from the vacuum pump. Typically, the two linesare sealed relative to the interior of the trap so that a “reservoir” offluid can be accumulated within the trap while an air space is providedabove the “reservoir” of fluid to conduct an air flow therethrough. Oneof the problems with such a trap is that the trap must be maintainedvertical as the trap operates under gravity. Accordingly, care must betaken to ensure that the trap does not turn upside down, as otherwise,fluid would immediately pass into the vacuum pump thereby rendering thepump inoperative.

It has also been known to place filters in the suction tube lines inorder to prevent fluid coming from an eyeball to pass onto the vacuumpump. However, one problem associated with this technique is that as theeyeball side of the filter become filled with fluid, the resistance inthe line to air flow increases. Thus, instead of the vacuum rising to 24inches of mercury at the eyeball, a smaller vacuum force is generated atthe ring-eyeball interface with the risk that a good cut in theepithelium may become compromised.

Another problem which may arise during an operation is that which isassociated with a slight movement of the ring from the eyeball throughaccident or inadvertence which may cause a slight break in the vacuumdue to a separation between the ring and the eyeball. Should this occur,an alarm would be sounded or visually indicated to the surgeon so thatthe ring may be reoriented and re-attached to the eyeball. However, if afilter has been provided in the suction line which has become filledwith fluid on the eyeball side, the recovery time for the reengaging thering with the eyeball is prolonged. In such a case, an eyeball movementcan occur.

Accordingly, it is an object of the invention to reduce the risk ofinterrupting a photoretractive keratectomy laser operation due to a lossof vacuum caused by an accumulation of fluid in a vacuum pump.

It is another object of the invention to preclude an accumulation offluid in a vacuum pump for instruments used in photoretractivekeratectomy laser surgery.

It is another object of the invention to be able to trap fluid in asuction line set for a keratome without significantly increasing theresistance to air flow in the suction line.

Briefly, the invention provides a fluid absorber for a suction tube setfor a keratome wherein the fluid absorber comprises a hollow housing forconnection at one side to a vacuum pump and for connection at anopposite side to the keratome and a formed absorbent mass in the housingfor absorbing fluid emanating from an eyeball without increasing theresistance to air flow at saturation by more than 3 inches of mercury.Typically, the absorbent mass is a cellulosic sponge mass.

In addition, the housing has a cap at each end with a spigot to receiveeither a suction tube or an inlet tube as the case may be. In addition,the fluid absorber includes a pair of spacer tubes, each of which islocated between the sponge mass and the respective cap. These spacertubes serve to space the sponge mass away from the spigot openings inthe end caps in order to avoid clogging of the spigots. In addition, thespacer tubes serve to compress the sponge mass therebetween. Thiscompression not only expands the sponge mass radially to engage againstthe inner diameter of the housing and close any space therebetween butalso eliminates any through passage through the cells of the sponge massfrom one end to the other.

In another embodiment, the sponge mass may be fixedly secured to thehousing, for example by means of an adhesive at each end thereof, inorder to prevent sliding of the sponge mass within the housing under asuction force of the vacuum pump.

The invention also provides a suction tube set which is comprised of thefluid absorber, a suction tube connected to one end of the housing ofthe fluid absorber for drawing a vacuum force within the housing and aninlet tube connected to and extending from an opposite end of thehousing of the fluid absorber for conveying a vacuum force therethrough.

The suction tube set is connected to and between an eyepiece for fittingagainst an eyeball and a vacuum pump for drawing a vacuum at theeyepiece-eyeball junction. For example, the eyepiece may be the ring ofan automated disposable keratome as sold by LaserSight Technologies Inc.of Winter Park, Fla. This ring is sized to engage an eyeball and has aplurality of ports for communicating with a passageway in the inlettube.

The absorbent mass is particularly characterized in being able to absorbfluid without increasing the resistance to air flow by no more than 2inches to 5 inches of mercury (Hg). The amount of fluid which isabsorbed by the absorbent mass is based upon the expected amount offluid which would be generated during an operation and by the amount ofresistance created by a fluid-filled mass. That is to say, the absorbentmass is characterized in being able to absorb the amount of fluidexpected to be generated during an operation without significantlyincreasing the resistance to air flow through the absorbent mass.

The purpose of forming a gap between the caps of the housing and thesponge mass is to avoid the sponge covering over the apertures of therespective caps which communicate with the suction line, as otherwise,the resistance to air flow could increase significantly thereby giving afalse high value at the vacuum pump to a surgeon that the eyeball towhich the eyepiece is locked may have become released and may havemoved. In addition, a significant increase in air flow resistance wouldsignificantly increase the response time should vacuum be lost at theeyeball-eyepiece junction. This would also negate a safety pressuredifferential system at the vacuum pump which would notify the surgeonthat vacuum has been lost.

Where the absorbent mass is a cellulosic sponge mass, it has been knownto manufacture such sponges with an anti-bacterial agent in order toprevent the growth of mold and the like. In accordance with theinvention, the cellulosic sponge mass is compressed to squeeze out theantibacterial agent. Further, compression of the sponge mass reduces thechance that there may be a continuous passage through the sponge massfor a flow of fluid. Typically, the sponge mass can be gamma sterilizedto achieve a sterile product.

Further, it has been found that compression of the cellulosic spongemass has little effect on the air flow resistance through the spongemass.

Typically, the cellulosic sponge mass is hydrophillic and iscommercially available under the trademark OCELLO and is sold by the 3MCompany. Other types of sponge material may be polyurethane,hydrophillic polyethylene and polypropylene.

These and other objects and advantages of the invention will become moreapparent from the following detailed description taking in conjunctionwith the accompanying drawings wherein:

FIG. 1 illustrates a broken view of the fluid absorber constructed inaccordance with the invention;

FIG. 2 illustrates a cross-sectional view of the absorbent mass withinthe housing of the fluid absorber;

FIG. 3 illustrates an exploded view of the fluid absorber of FIG. 1;

FIG. 4 illustrates a schematic view of the suction tube setincorporating the fluid absorber and connected to an eyepiece at one endand to a vacuum pump at an opposite end;

FIG. 5 illustrates a perspective view of the eyepiece; and

FIG. 6 illustrates an end view of the eyepiece.

Referring to FIG. 1, the fluid absorber 10 is comprised of a hollowedhousing 11 of tubular shape and a formed absorbent mass, such as acompressed cellulosic sponge mass 12 in the housing 11 for absorbing afluid volume. As shown in FIG. 4, a suction tube 13 is connected to oneend of the fluid absorber 10 for drawing a vacuum force within thehousing 11 and an inlet tube 14 is connected to and extends from anopposite end of the fluid absorber 10 for conveying a vacuum forcetheretrough. The resulting suction tube set typically has a length ofabout 7 feet and is intended to be disposed of after a single use.

Referring to FIGS. 1 and 2 the housing 11 is constructed of an open endtube or barrel 15, for example, of clear, plastic material. By way ofexample, the barrel 15 has an inside diameter of 0.730 inches and alength of 1.5 inches.

As shown in FIGS. 1 and 3, the housing 11 also has an end cap 16 securedto one end of the barrel 15 and a second end cap 17 secured to thebarrel 15 at the opposite end. Each end cap 16, 17 includes an outer rim18 and an inner rim 19 to define a circumferential recess into which thebarrel 15 fits. In addition, each end cap 16, 17 has a coaxial spigot20, 21 extending on an opposite side from the rims 18, 19. Each end cap16, 17 also has a hollow stem 22 facing inwardly of the barrel 15 whichis of axial extent equal to the axial length of the inner rim 19 of theend cap 17.

Each end cap 16, 17 is sized so that the barrel 15 is slidably mountedon the outside diameter of the inner rim 19 of each. A suitable adhesiveis also provided to secure each end cap 16, 17 to the surface of thebarrel 15. By way of example, the adhesive may be a Loctite U.V.adhesive 3311-300 cP.

The spigot 20, 21 of each end cap 16, 17 is slightly tapered in aconventional manner to receive the respective tube 13, 14, as indicatedin FIG. 4.

The sponge mass 12 is disposed within the barrel 15. In addition, a pairof spacer tubes 23 are disposed within the housing 11 with each tube 23being disposed between the sponge mass 12 and a respective end cap 16,17. During assembly, the sponge mass 12 is first placed within thebarrel 15 as indicated in FIG. 2. Thereafter, as indicated in FIG. 3, apair of spacer tubes 23 and the end caps 16, 17 are moved into and overthe ends of the barrel 15. During this time, the spacer tubes 23compress the sponge mass 12. As a result, the sponge mass 12 islongitudinally compressed while being radially expanded against theinner periphery of the barrel 15. The result is that any throughpassageway through the sponge mass 12 is broken up and eliminated and,at the same time, the sponge mass 12 is sealed against the innerperiphery of the barrel 15 so that there are no pathways formed betweenthe sponge mass 12 and the barrel 15.

The sponge mass 12 is formed, for example, by four coaxially disposedsections of sponge material which are compressed when assembled into thebarrel 15.

The fluid absorber 10 in the suction tube set serves to absorb fluid(tears) passing to the absorber without increasing the resistances toair flow at saturation by more than 3 inches Hg.

Once assembled, the fluid absorber 10 is fitted with the suction tube 13and inlet tube 14. The suction tube 13 may also be fitted with aconnector of conventional structure, such as a Colder-DSM-2202, forconnection to a vacuum pump 24 (see FIG. 4) in a conventional manner. Inaddition, the inlet tube 14 is connected to a keratome instrument 25.

Typically, the suction tube 13 is made of polyvinylchloride havingdimensions of ¼″×⅛″×4″. The inlet tube 14 is similarly made ofpolyvinylchloride with dimensions of {fraction (3/16)}″×⅛″×84″. Theoverall length of the two tubes 13, 14 is seven feet.

The sponge pieces employed within the housing 11 each have an initialuncompressed thickness of ⅝″ and an outside diameter of ¾″. In thecompressed state, the axial length of the sponge mass 12 is slightlyless than the axial length of the barrel 15 i.e. slightly less than1.5″. Thus, the four sponge pieces are reduced from an overall length of2.5″ to about half of that length.

Referring to FIG. 5, the keratome 25 is constructed, as is known, forfitting against an eyeball 26 and is typically provided with an end ring27 of curved contour having a plurality of circumferentially disposedports 28 through which air can be drawn. (See FIG. 6). These ports 28are thus in communication with a passageway in the inlet line 14.

When a surgeon is to operate on the eyeball of a patient, the end ring27 of the eyepiece 25 is brought into contact with the eyeball 26 andvacuum drawn on the eyepiece 25 so that the suction force effectedthrough the ports 28 in the end ring 27 of the eyepiece 25 locks theeyeball 26 and end ring 27 together. Thus, the surgeon is able toperform a surgical procedure on the eyeball 26 on the assumption thatthe eyeball will remain fixed in place. For example, in the case of anautomated disposable keratome, as noted above, a blade (not shown) maybe activated to effect the slicing of a flap in the epithelial layer ofthe eyeball. Thereafter, use is made of a laser beam to ablate cornealtissue.

Typically, a low vacuum pressure, for example at 8″ or less of mercury(Hg) is used to lock the eyepiece 25 to the eyeball. The locking effecttakes place over milliseconds.

As tearing occurs during the surgical procedure, any fluid, i.e. saltwater, emanating from the eyeball 26 into the end ring 27 via the ports28 migrate down the inlet tube 14 and eventually into the fluid absorber10. The compressed cellulosic sponge mass 12 of the absorber 10 willthen absorb the fluid volume. For example, a typical surgical procedurewill produce up to 0.5 cubic centimeters of fluid. The sponge mass 12has a capacity of absorbing 1.5 cubic centimeters of fluid therebyproviding an adequate safety factor while providing a minimal resistanceto air flow so that the vacuum pump 26 is able to continue to operate atthe vacuum pressure of 24 inches of mercury (Hg). Upon saturation of thecompressed sponge mass 12, resistance to air flow increases slightly.

The capacity of the sponge mass 12 to absorb fluid without a significantincrease in resistance to air flow allows a surgical procedure tocontinue under normal conditions. Typically, the amount of fluid to beadsorbed by the compressed sponge mass 12 is less than that which isreasonably expected during a surgical procedure.

The invention thus provides a disposable fluid absorber for absorbing afluid volume within a suction tube set used with a keratome for lasereye surgery without significant increase in resistance to air flow.

The fluid absorber may be employed without regard to a vertical orhorizontal disposition as the forces of gravity are not of anyconsequence in the functionality of the absorber.

While the sponge mass 12 has been described as a compressed cellulosicsponge mass, it is understood that other types of materials may also beused provided the materials satisfy the characteristic of absorbing anamount of fluid while increasing the resistance to air flow atsaturation by only a small amount.

The suction tube set is characterized by having a low inherent pressuredrop. When disconnected with the one end free and exposed to the room,the vacuum created at the entrance to the vacuum pump is approximately7-8 inches of mercury. When connected to the eyepiece and there is noair leakage into the system, the vacuum pump will typically draw 26inches plus of mercury.

A unique characteristic of this suction tube set is the ability toabsorb quantities of a person's tears (salt water) with little change inresistance to air flow. Hence, after the fluid absorber has absorbede.g. ½ cc of tears, the open line will still exhibit a vacuum of 8-10inches of mercury.

This condition provides two advantages over suction lines containingfilter traps which are generally the system of choice due to theirinherent nature of positively preventing fluid from entering the vacuumpump and thereby destroying it's ability to continue to function. Thefirst advantage is that the fluid absorber may absorb quantities oftears with minimal increase in resistance to air flow. The secondadvantage is the inherent low resistance to flow of the system.

The results of these advantages are the laser equipment can beprogrammed such that when resistance (negative pressure) at the vacuumpump inlet drops due to loss of suction at the connection between theeyeball 26 and suction ring 27, it will become immediately evident for alow vacuum pressure (below 15 inches of mercury) will instantaneouslyappear at the entrance to the vacuum pump. This pressure sensitivity canbe translated into a signal which can inform the practitioner or whenconnected to the laser (surgical knife) will immediately shut the systemdown before harm can occur to the person's eye due to potential eyemovement. (Improper cutting, cutting in the wrong area, etc.) The secondadvantage is that vacuum recovery when suction is lost due to leakagebetween the suction ring 27 and the eyeball 26 is significantly fasterthan suction systems using lower air flow due to higher line resistance.This reduces the likelihood of improper cutting or otherwise causingthis medical procedure to result in poorer results than expected.

What is claimed is:
 1. A fluid absorber for a suction tube set for akeratome, said fluid absorber comprising a hollow housing for connectionat one side to a vacuum pump and for connection at an opposite side to akeratome; and a formed absorbent mass in said housing for absorbing afluid without increasing the resistance to air flow at saturation bymore than 3 inches of mercury.
 2. A fluid absorber as set forth in claim1 wherein said absorbent mass is a cellulosic sponge mass.
 3. A fluidabsorber as set forth in claim 2 wherein said housing has a first cap atone end with a spigot to receive a suction tube and a second cap/at theopposite end with a spigot to receive an inlet tube and which furthercomprises a first spacer tube between said sponge mass and said firstcap and a second spacer tube between said sponge mass and said secondcap.
 4. A fluid absorber as set forth in claim 3 wherein said spongemass is compressed by and between said spacer tubes.
 5. A suction tubeset comprising a hollowed housing of tubular shape; a formed absorbentmass in said housing for absorbing a fluid whithout increasing theresistance to air flow at saturation by more than 3 inches of mercury; asuction tube connected to one end of said housing for drawing a vacuumforce within said housing; and an inlet tube connected to and extendingfrom an opposite end of said housing for conveying a vacuum forcetherethrough.
 6. A suction tube set as set forth in claim 5 wherein saidabsorbent mass is a compressed sponge mass.
 7. A suction tube set as setforth in claim 6 wherein said compressed sponge mass is characterized inabsorbing no more than 1.5 cubic centimeters of fluid.
 8. A suction tubeset as set forth in claim 6 wherein said compressed sponge mass isformed of a plurality of axially disposed layers.
 9. A suction tube setas set forth in claim 7 wherein said housing has a first cap at one endwith a spigot receiving said suction tube, and a second cap at anopposite end with a spigot receiving said inlet tube.
 10. A suction tubeset as set forth in claim 9 which further comprises a first spacer tubebetween said compressed sponge mass and said first cap and a secondspacer tube between said compressed sponge mass and said second cap. 11.A suction tube set as set forth in claim 9 wherein said housing has atubular barrel secured to and between said caps.
 12. A suction tube setas set forth in claim 11 wherein said barrel is made of a thintransparent plastic.
 13. A suction tube set as set forth in claim 5wherein said mass is spaced from said first cap to define a gaptherebetween and is spaced from said second cap to define a gaptherebetween.
 14. A suction tube set as set forth in claim 13 whereinsaid mass is secured in said housing at each of two opposite endsthereof to prevent movement of said mass within said housing againstsaid end caps.
 15. A suction tube set comprising a housing having afirst spigot at one end and a second spigot at an opposite end; asuction tube mounted on said first spigot of said housing to draw asuction force within said housing; an inlet tube mounted on said secondspigot of said housing to convey a suction force therethrough; and aformed absorbent mass in said housing for absorbing a fluid volumepassing through said housing from said inlet tube without increasing theresistance to air flow at saturation by more than 3 inches of mercury.16. A suction tube set as set forth in claim 15 wherein said formedabsorbent mass has a capacity to absorb 1.5 cubic centimeters of fluid.17. A suction tube set as set forth in claim 15 wherein said absorbentmass is